Means to prevent excessive frictional loading in a wire printer



Feb. 7, 1967 R. D. NELSON 3,302,562

MEANS TO PREVENT EXCESSIVE FRICTIONAL LOADING IN A WIRE PRINTER FiledJune 29, 1964 2 Sheets-Sheet 1 INVENTOR.

ROLAND D. NELSON ATTORNEY Feb. 7, 1967 NELSON 3,302,562

MEANS TO PREVENT EXCESSIVE FRICTIONAL LOADING IN A WIRE PRINTER FiledJune 29, 1964 2 Sheets-Sheet 2 FIG. 4

United States Patent f 3,302,562 MEANS TO PREVENT EXESSIVE FRICTIONALLOADING IN A WERE PRINTER Roland D. Nelson, San Jose, Calif., assignorto International Business Machines Corporation, New York, N.Y., acorporation of New York Filed June 29, 1964, Ser. No. 378,616 11 Claims.(Cl. 101-103) This invention relates to wire printers and, moreparticularly, to print head assemblies.

A problem has long existed in wire printers of increased frictionalloading of the mechanism over a period of operation due to ink from theribbon working its way into the space between the print wire and itsguide tube. The sliding motion of the wire causes the ink to work itsway from the print end of the print wires throughout the entire lengthof the wire and the tube to the setup mechanism. The resultant highfriction causes excessive wear of the actuating device and the otherparts of the system and also appreciably increases the operative forcerequired to operate the printer. As the speed of operation of wireprinters has increased, the excessive wire friction caused by the inkhas become an even greater problem since it is more diflicult to drivethe wires at the rate required. It is therefore the principal object ofthis invention to provide a printing apparatus which prevents ink andother foreign matter from entering the working area of the printmechanism.

It is another object of this invention to provide a printing apparatuswhich is adapted to use in a high speed printer and which is reliable inoperation.

It is a further object of the invention to provide a print head assemblythat is usable in high speed printers which utilize springs to providethe force to actuate the print mechanism.

Briefly, according to the invention, a print mechanism is providedcomprising a plurality of selectively axially displaceable characterforming elements, wherein a portion of the character forming elementspasses through an enclosure and wherein a fluent material is disposedwithin the enclosure and is subjected to pressure to provide a sealaround each character forming element so that ink, card dust, and otherforeign matter is blocked from moving from the character forming ends ofthe character forming elements to the printer operating mechanism.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention, as illustratedin the accompanying drawings.

FIG. 1 is a perspective view, partly in section along lines AA of FIG.4, of a print head assembly embodying the invention;

FIG. 2 is a 90-degree segment of the control cam of the wire printer ofFIG. 3;

FIG. 3 is a perspective view of a wire printer utilizing a plurality ofthe print head assemblies shown in FIG. 1;

FIG. 4 is an end view of the print head assembly.

In accordance with the invention, the print mechanism comprises a printhead comprising a housing having hollow portions 12 through which theprint guide tubes 14 are inserted and fixed into position in the properalignment. Character forming wires 16 are mounted within the guide tubes14 so that by selective axial displacement of the print wires 16 acharacter is formed, and the selected character is recorded on recordmember 18 by driving the character forming ends 20 of the print wiresagainst an inked ribbon 22, record card 18, and a relatively fixedplaten member (not shown). The wire print head 10 is provided with areservoir or cavity 24 through which print wires 16 pass from the endsof guide tubes Patented Feb. 7-, l67

14 to the print wire guide matrix 26 formed in the print head face. Afluent material is injected into the cavity and subjected to pressure sothat the fluent material closely surrounds the portion of the printwires extending through the cavity.

The fluent material consists of a mixture of three components, a flowrestricting material, a filler material, and a bonding material. Theparticle size of the flow restricting material must be small enough topermit entry between the wires in the matrix, but large enough toprevent entry of the mixture between print wires 16 and their guidetubes 14. Also, the material must be chemically inert and have a lowcoeflicient of friction. A nylon powder has been found suitable for theflow restricting material of the mixture. The filler powder must be ofvery small particle size to seal 01f the pores in the flow restrictingpowder and thereby prevent ink from flowing through the material. Thefiller powder also must be chemically inert and have a low coefficientof friction. Polyethylene powder has been found suitable for the fillermaterial. A chemically inert bonding material must be used to seal thesmall pores of the mixture of the filler powder and the flow restrictingpowder and to improve the flow characteristics of the mixture. Asilicone grease, such as that manufactured under the trade name of DowCorning No. 3, has been found suitable. The proportions of the threecomponents of the fluent material can be determined experimentally for aparticular application, and equal volume of each of the three componentshas been found to be one suitable mixture.

The fluent material is pressurized to insure that the material closelysurrounds each of print wires 16, and the small reservoir provides asuflicient quantity of the fluent material to compensate for leakage,wear and thermal expansion. In the embodiment shown, the fluent materialis injected into the cavity through a loading opening 40, and a bleedhole 42 is provided to aid in the removal of excess material. When thecavity is first loaded, the material is added until an excess isextruded at bleed hole opening 42. Bleed hole opening 42 is then closedas by the application of a tight fitting screw 43, and the fluentmaterial is then pressurized by applying a force to a tight fittingpressure piston 44 which is inserted within loading opening 40. A secondbleed hole 46 is provided to remove excess fluent material, and thematerial is maintained under pressure by a pressure spring 48 held inposition by a suitable means such as a set screw 50 applied in loadingopening 40. A balance in the pressure used may be determinedexperimentally from the opposing consideration of complete stoppage ofink flow by a high pressure and the increased frictional forces on theprint wires by the high pressure of the fluent material. In practice, apressure of approximately 45 pounds per square inch has been foundsuitable since this pressure completely stops the flow of ink fromreaching guide tubes 14 and produces a frictional drag on each wire ofapproximately ten grams force, which is not objectionable in theembodiment shown. If the friction force is too high, the print wires mayfail to operate dynamically at full speed.

In a specific printer mechanism, the print wires have an outsidediameter of .008 inch, and these wires operate in a guide tube having a.010 inch inside diameter. The wires are set on .015 inch centers sothat a nominal .007 inch gap is present between wire surfaces as theypass through enclosure 24. For this mechanism a flow restrictingmaterial consisting of a nylon powder having a particle size of .002 to.007 inch is suitable. The filler powder consists of polyethylene powderhaving a particle size of 500 microns, and the bonding material consistsof a silicone grease. The components of the fluent material are combinedin equal volume.

A diagrammatic view of a Wire printer embodying the invention is shownin FIG. 3. A platen member (not shown) backs up a suitable recordingmaterial, such as a ribbon 22, disposed opposite the record member andthe platen member. The character forming ends 20 of a plurality of printwires 16 are positioned on the other side of the ribbon. The print wires16 are slideably supported in guide tubes 14 which converge at the printends of the wires to form a print head 10. The print heads are movablymounted by bracket 15 so that each printhead is operator adjustable toprovide printing of a line in any location on record card 18. The otherends of the guide tubes and wires fan out, and the wires 16 are attachedto a wire setting mechanism. The wire setting mechanism comprises a cam28 which controls the movement of bell cranks 30 which comprisearmatures for magnetic holding means 33. When the armatures 30 arereleased by magnetic bucking coils 32, the motive force for driving theprint wires to the operative position is supplied by a resilient means,such as coil springs 34. The contour of the cam is provided with a wiresetup portion 36 and a printing portion 38. The print data is providedby suitable electronic control circuitry (not shown), and the operationis timed so that at the zero point in FIG. 2 the release of thecharacter forming elements comprising the selected character isinitiated. This operation is performed by electronically selectingindividual bucking coils 32 to buck out the flux generated by the holdcoil 33 so that the bell crank is released to wire setup portion 36 ofthe cam. The print cam controls the character setup, regulates theimpact of the wires, and restores the armatures to the hold magnet afterprinting. The released armatures have stabilized by the start of theprint zone 38 of the cam, and the bell cranks are driven by the force ofthe springs 34 so that the print ends of the character forming elementsare moved to the print position to impress the selected character uponthe record member.

Thus, it can be seen that there is provided a print head assembly tosolve the problem of excessive friction caused by ink and other foreignmaterial being moved into the operating mechanism of a wire printer. Theprint head assembly possesses small size, low inertia, and highmobility, so that it is suitable for solving this problem in not onlythe wire printer shown in the drawings but also in wire printers of thetype shown in U.S. Patents 2,580,- 788, 2,785,627 and 2,802,414.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that the foregoing and other changes in theform and details may be made therein without departing from the spiritand scope of the invention.

What is claimed is:

1. A wire printing mechanism, comprising:

an enclosure;

a plurality of selectively movable character forming elements havingfirst character forming portions and having second portions thereofpassing through said enclosure;

a fluent material disposed in said enclosure surrounding said secondportions of said character forming elements; and

pressure forming means to pressurize said fluent material in saidenclosure to block the passage of foreign material from said characterforming portions beyond said second portions of said character formingelements.

2. In a recording device:

a plurality of character forming elements selectively actuable formoving the character forming ends into and out of engagement with arecord medium;

a fluent material;

means for positioning said fluent material to surround a portion of saidcharacter forming elements; and

means for applying pressure to said fluent material so that the movementof foreign material along the character forming elements from saidcharacter forming ends is limited thereby.

3. A printing transducer, comprising:

a plurality of character forming elements mounted within guide means,each of said character forming elements having character forming endsextending from said guide means;

a housing having a cavity filled with a fluent material;

means for mounting the character forming elements within said housing sothat a portion of each of the character forming elements extending fromsaid guide means passes through said fluent material; and

pressure forming means to apply pressure to said fluent material toprevent foreign material from moving along said character formingelements to said guide means.

4. A printing transducer, comprising:

a plurality of character forming elements mounted within guide means,each of said character forming elements having character forming endsextending from said guide means;

a housing having a cavity filled with a fluent material, said fluentmaterial comprising a mixture of plastic powders and a bonding material;

means for mounting the character forming elements within said housing sothat a portion of each of the character forming elements extending fromsaid guide means passes through said fluent material; and

pressure forming means to apply pressure to said fluent material toprevent foreign material from moving along said character formingelements to said guide means.

5. A printing transducer, comprising:

a plurality of character forming elements mounted within guide means,each of said character forming elements having character forming endsextending from said guide means;

a housing having a cavity filled with a fluent material said fluentmaterial comprising a fiow restricting material, a filler material, anda bonding material;

means for mounting the character forming elements within said housing sothat a portion of each of the character forming elements extending fromsaid guide means passes through said fluent material; and

pressure forming means to apply pressure to said fluent material toprevent foreign material from moving along said character formingelements to said guide means.

6. A wire printing mechanism, comprising:

an enclosure;

a plurality of selectively movable character forming elements havingfirst character forming portions and having second portions thereofpassing through said enclosure;

a fluent material disposed in said enclosure surrounding said secondportions of said character forming elements. said fluent materialcomprising a mixture of plastic powders and a bonding material; and

pressure forming means to pressurize said fluent material in saidenclosure to block the passage of foreign material from said characterforming portions beyond said second portions of said character formingelements.

7. A wire printing mechanism, comprising:

an enclosure;

a plurality of selectively movable character forming elements havingfirst character forming portions and having second portions thereofpassing through said enclosure;

a fluent material disposed in said enclosure surrounding said secondportions of said character forming elements, said fluent materialcomprising a flow restricting material, a filler material, and a bondingmaterial; and z pressure forming means to pressurize said fluentmaterial in said enclosure to block the passage of foreign material fromsaid character forming portions beyond said second portions of saidcharacter forming elements.

8. A wire printing mechanism, comprising:

an enclosure;

a plurality of selectively movable character forming elements havingfirst character forming portions and having second portions thereofpassing through said enclosure;

a fluent material disposed in said enclosure surroundin g said secondportions of said character forming elements, said fluent materialcomprising a mixture of plastic powders and a bonding material;

pressure forming means to pressurize said fluent material in saidenclosure to block the passage of foreign material from said characterforming portions beyond said second portions of said character formingelements; and

resilient means to drive selected ones of said character formingelements to a record marking position.

9. A Wire printing mechanism, comprising:

an enclosure;

a plurality of selectively movable character forming elements havingfirst character forming portions and having second portions thereofpassing through said enclosure surrounding said second portions of saidcharacter forming elements;

a fluent material disposed in said enclosure, said fiuent materialcomprising a flow restricting material, a filler material, and a bondingmaterial;

pressure forming means to pressurize said fluent material in saidenclosure to block the passage of foreign material from said characterforming portions beyond said second portions of said character formingelements; and

resilient means to drive selected ones of said character formingelements to a record marking position.

10. A wire printing mechanism, comprising:

a housing having a central enclosure and a plurality of openingsthereto;

a plurality of selectively movable character forming elements mounted insaid omnings, said character forming elements having first characterforming portions extending beyond said enclosure and having secondportions thereof passing through said enclosure;

a fluent material comprising a mixture of plastic powders and a bondingmaterial;

&

means for loading said fluent material into said enclosure surroundingsaid second portions of said character forming elements;

pressure forming means to pressurize said fluent material in saidenclosure to block the passage of foreign material from said characterforming portions beyond said second portions of said character formingelements; and

resilient means to drive selected ones of said character formingelements to a record marking position.

11. A wire printing mechanism, comprising:

a housing having a central enclosure and a plurality of openingsthereto;

a plurality of selectively movaible character forming elements mountedin said openings, said character forming elements having first characterforming portions extending beyond said enclosure and having secondportions thereof passing through said enclosure;

a fluent material comprising a mixture of nylon powder,

polyethylene powder and silicone grease;

means for loading said fluent material into said enclosure surroundingsaid second portions of said character forming elements;

pressure forming means to pressurize said fluent material in saidenclosure to :block the passage of foreign material from said characterforming portions beyond said second portions of said character formingelements; and

resilient means to drive selected ones of said character formingelements to a record marking position.

References Cited by the Examiner UNITED STATES PATENTS 2,712,862 7/1955Pemberton 188-205 2,785,627 3/1957 Johnson 101-93 2,787,952 4/1957 Roche10193 2,928,338 3/1960 Wockenfuss 101-93 3,087,420 4/1963 Brehm 10193References Cited by the Applicant UNITED STATES PATENTS 1,056,010 3/1913Dailey. 2,712,862 7/1955 Pemberton. 2,928,338 3/1960 Wockenfuss.

5O WILLIAM B. PENN, Primary Examiner.

1. A WIRE PRINTING MECHANISM, COMPRISING: AN ENCLOSURE; A PLURALITY OFSELECTIVELY MOVABLE CHARACTER FORMING ELEMENTS HAVING FIRST CHARACTERFORMING PORTIONS AND HAVING SECOND PORTIONS THEREOF PASSING THROUGH SAIDENCLOSURE; A FLUENT MATERIAL DISPOSED IN SAID ENCLOSURE SURROUNDING SAIDSECOND PORTIONS OF SAID CHARACTER FORMING ELEMENTS; AND PRESSURE FORMINGMEANS TO PRESSURIZE SAID FLUENT MATERIAL IN SAID ENCLOSURE TO BLOCK THEPASSAGE OF FOREIGN MATERIAL FROM SAID CHARACTER FORMING PORTIONS BEYONDSAID SECOND PORTIONS OF SAID CHARACTER FORMING ELEMENTS.